Interleukin-4 (IL-4), IL-4 mutants and its soluble receptors are being tested in the clinic by systemic injection or by gene transfer using viral vectors for the treatment of rheumatoid arthritis, bronchial asthma, and cancer Studies are underway to characterize the structure, function, signal transduction and targeting of receptors (R) for IL-4 and IL-13, a IL-4 related cytokine, on immune and cancer cells. Reconstitution studies have confirmed that IL-13R alpha'chain, but not alpha chain, is a novel component of the IL-4R system. These studies have demonstrated that IL-4R beta chain is a neccessary component of IL13R system. Thus, IL-4R and IL-13R share IL4R beta and IL-13R alpha' chains. These studies help explain the similar biological activities of IL-4 and IL-13 on many different cell types including cancer cells. 2) To understand the molecular mechanism of signal transduction by the IL-4 and IL-13 receptor, we have studied the phosphorylation and activation of JAK kinases and signal transduction activator of transcription (STAT) intracellular proteins. Our studies demonstrate that both IL-4 and IL-13 can utilize similar tyrosine kinases, however, some differences exist. IL-4 phophorylates JAK1 and JAK3 in cells that express IL-4R beta and IL-2R gamma chain and it phosphorylates JAK1 and JAK2 in cells that express IL-13R alpha' and IL-4R beta chain. IL-13 phosphorylates JAK1 and JAK2 in cells that express IL-13R, however, it does not phosphorylate JAK3. In all combinations, both IL-4 and IL-13 activate same STAT-6 protein. These studies explain why IL-4 and IL-13 have redundant effects on a variety of cell types. Reconstitution experiments have demonstrated that IL-4R beta and IL-13R alpha'chain is required for JAK2 phosphorylation by IL-4 and then activation of STAT-6 protein. Additional experiments are underway to examine the association of JAK kinases with various chains of IL-13R system. 3) The IL-4 and IL-13R directed targeting of a Pseudomonas exotoxin, Diphtheria toxin, or alternatively receptor directed gene transfer is also being investigated. The receptors for these two interleukins are expressed in abundance on human tumor cells that offer an attractive target for toxin therapy or gene therapy. In vivo experiments in immunodefeicient mice with human AIDS-associated Kaposi's sarcoma tumors have demonstrated complete responses in a dose dependent manner in response to IL4-toxin administration. Treatment of these immunodeficient animals with IL-4 toxin also corrected metabolic changes and constitutive symptoms such as weight loss caused by growing tumors. Preclinical pharmacokinetics and toxicology studies are underway to fully appreciate its potenial for the management of persons with AIDS Kaposi's sarcoma tumors. Our previous studies on IL-4R targeting resulted in a Phase I clinical trial for malignant gliomas. This trial is now ongoing at nine Centers in the United Sates and three Centers in Germany. These clinical studies will help elucidate the safety and efficacy of this and other chimeric toxins being tested in clinic under various INDs.